Essential a super good voltmeter , 2 signal generators , a dusl input scope , a frequency counter and a lesser voltmeter , but still 4 digits.
I will pass along that i have a small secondary scope for audio work. It's called a DSO 201 , it's the sixe of a small player , has a decent probe . Goes to 1 mhz. The kit fits in a shirt pocket : note that if you have one check the upgrade to the 4.22 series firmware , it works a lot better. So for audio it all fits in my small case with the computer that is very convenient. For larger or more complex work , the good old textronix is still the one tool i go back to .I do mostly Audio/Visual and RF work. That's why i got two generators , one rf the other is audio. Good tools do good work. Never hesitate to put the money on a good tool , that applies to good testing equipment. The well constructed and calibrated instruments rule our benches.Calibrate often and keep em in good shape. Replace the leads often as they dry and crack and may become a danger after a number of years. Follow the first rule : use caution whenever you play in electronic/electric equipment . Safety First !